WareLogging, of a sort. IRC is the granddaddy of nearly all functional text-based chat systems on the Internet. It uses a client / server model: You get whichever client suits your fancy, and connect to a server where you can message other users directly and join "channels" to talk with a group. This design apparently draws some inspiration from CitizensBandRadio, and anticipates the useful features of most instant messaging clients.
IRC played a big role in early p2p file trading, and probably still sees massive infringing use. It was the first place I ever saw an mp3 or a ripped DVD movie.
= software =
* [http://www.mirc.co.uk/ mIRC], a Windows IRC client, is still probably my favorite application of all time. Closed source shareware, but uncrippled. Feature rich, pleasant to look at, and beautifully balanced. Sports a scripting engine with hooks into most of the app's functionality, and even a passable IDE. The aesthetic depends heavily on fixedsys, my favorite old-school font.
* KVirc - is this still around? A decent mIRC-alike for KDE.
= events.scifi.com =
Back in the day, the SciFiChannel used to run an IRC server at events.scifi.com. events was actually a crippled successor of sorts to icarus.scifi.com, which ran more functional software. Between about mid-1996 and '99, I spent more time on both servers than you would probably believe if I told you.
Although events was home to a fairly dedicated community (which I would guess peaked at 30 or 40 regulars), the SFC's only rationale for running the thing was using it to host occasional celebrity chats (including, if I remember right, a couple of "online science fiction conventions"), and in due course it was overrun with script kiddies while pretty much everyone worth talking to gave up and faded away, a process vastly accelerated by A) the impossibility of operating a channel with the normal administrative features disabled, B) an actively hostile Sci-Fi Channel, and C) the sort of weird little interpersonal soap operas that play out in those parts of the 'net where everyone really does craft a new identity behind some pseudonym.
Excellent summary.
Also, Brennen, Saalon, and I all met on events. Brennen and I could immediately finish each other's sentences, while Saalon had started some fascinating online fiction projects that Brennen and I joined.